JPH06227854A - Production of formed ceramic article - Google Patents

Abstract

PURPOSE:To obtain a forming for the production of a ceramic article having complicate shape and required to have high dimensional accuracy with few forming steps in a short time. CONSTITUTION:Slurry is produced by mixing 100 pts.wt. of inorganic powder composed of 50-97wt.% (preferably 70-90wt.%) of ceramic powder and 3-50wt.% (preferably 10-30wt.%) of rho-alumina powder with 15-50 pts.wt. (preferably 18-30 pts.wt.) of water. The slurry is injection molded into a non-water absorbing mold heated at 30-100 deg.C. The particle diameter of the above rho-alumina is 0.1-10mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ceramic molded body by injection molding a slurry in which ceramic powder and water are mixed to obtain a ceramic molded body.

[0002]

2. Description of the Related Art An injection molding method has been known as a conventional method for molding a ceramic product which is more complicated and more accurate. In this injection molding method, ceramic powder is mixed with a large amount of an organic binder composed of a resin such as polyethylene and polystyrene and a wax, and the mixture is kneaded, and the kneading raw material is heated to about 200 ° C. to be fluidized to obtain no water absorption. It is injected into the mold and cooled and solidified to produce a molded body. Then, a ceramic sintered body is obtained by degreasing the formed body and firing it.

[0003]

In the above-mentioned conventional injection molding method, since the fluidity sharply decreases with cooling in the mold, molding defects such as welds and flow marks are likely to occur. Moreover, in order to degrease the molded body without causing swelling or cracks, it was necessary to slow the temperature rising rate and to complete degreasing for a long time of 100 to 400 hours.
As a proposal for solving these drawbacks, there is a method in which a slurry containing no organic binder is poured into a mold cooled below the solidification temperature of the slurry and solidified to obtain a molded product (JP-A-60- No. 217106 “Inorganic powder freeze-molding method”), this method has a drawback that the amount of a dispersion medium such as water added is large and the permissible range is narrow. Furthermore, since the amount of the dispersion medium such as water added is large, there are problems that the strength of the molded body is low and the density of the fired product is low. Further, there is a drawback that a freeze-drying step is required before firing the molded product, which complicates the process and the apparatus.

The present invention solves the problems such as degreasing and molding defects existing in the above conventional injection molding method, and can obtain a molded body for a ceramic product which is complicated and requires high dimensional accuracy. It is an object to provide a method for manufacturing a body.

[0005]

The method for producing a ceramic molded body of the present invention is 50 to 97% by weight, preferably,
100 to 100 parts by weight of inorganic powder consisting of 70 to 90% by weight of ceramic powder and 3 to 50% by weight, preferably 10 to 30% by weight of ρ-alumina powder, 15 to 50 parts by weight of water,
Preferably 18 to 30 parts by weight are mixed to form a slurry,
This is a method for producing a ceramic molded body in which this slurry is injection-molded into a waterless type heated to 30 ° C to 100 ° C.

Further, a slurry containing 0.01 to 3 parts by weight of a dispersant such as a polycarboxylic acid type, a polyphosphoric acid type, a naphthalene sulfonic acid type, an amine type or an allyl sulfonic acid type is used. Further, if necessary, a water-soluble polymer as an organic binder, for example, polyvinyl alcohol, polyethylene glycol, polyacrylic acid amide,
0-5 parts by weight of sodium alginate, CMC and the like may be added, and a defoaming agent, a lubricant, a protective agent and the like may be added. The particle size of the ρ-alumina powder used here is 0.1 to 10 μm, preferably 0.5 to 3 μm, and as a molding slurry, it can be molded if its apparent viscosity is 10,000 cps or less, but it has a defoaming property. Taking into consideration, 1000 cps or less is more preferable.

The slurry is 30 to 100 ° C., preferably 6
It is injected into a non-water-absorbing mold made of metal, resin, wood, etc. heated to 0 to 80 ° C. to obtain a ceramic molded body.

After that, the obtained ceramic compact was
After being continuously dried, it is fired to produce a ceramics sintered body. The drying time of this molded product is 1/2 to 1/5 of the degreasing time of the conventional method. Further, the ceramics used in the present invention include alumina, zirconia, silicon nitride, silicon carbide, etc., and are not limited to the types of ceramics, and are appropriately selected and used according to required product characteristics and the like. It is something.

[0009]

The operation of the present invention is as follows.
The use of ρ-alumina as a binder. That is, it is known that ρ-alumina has a property of solidifying to share water with surrounding ρ-alumina particles when hydrated, and in the present invention, this phenomenon is positively applied to the method for producing a ceramic molded body. By applying it and using ρ-alumina as a binder or a hardening agent for ceramic materials, the problems of the conventional method are solved.

On the other hand, in the molding method outside the conditions of the method for manufacturing a ceramic molded body of the present invention, when the ceramic powder exceeds 97% by weight, that is, when the inorganic powder containing less than 3% by weight of ρ-alumina powder is used. However, since the amount of ρ-alumina as a binder is too small, the strength of the molded body is low and it is difficult to carry. Further, the ceramic powder is less than 50% by weight, that is, the ρ-alumina powder is 50% by weight.
When an inorganic powder in excess of wt% is used, the amount of ρ-alumina is too large, the viscosity is too high, the curing is fast, and the temperature distribution in the molded body during curing is not uniform, so that cracking easily occurs.
Further, in order to avoid this, it is necessary to keep the mold temperature low and slow the curing speed, which rather increases the curing time and deteriorates the productivity.

Further, if the added water is less than 15 parts by weight, it will be difficult to flow and molding will be difficult. On the other hand, when the amount of water exceeds 50 parts by weight, the strength of the molded body is low, the molded body is easily broken when taken out from the mold, and it is difficult to carry, the curing time becomes long, and the productivity decreases.

Further, when the temperature of the non-absorption type is less than 30 ° C., the solidification time of the sludge becomes very long, and when it exceeds 100 ° C., explosion at the time of solidification and dry cracking at the time of removing the solidified compact are frequent. Is unsuitable.

If the particle size of ρ-alumina exceeds 10 μm, a large number of pores are generated in the ceramic fired product and the density cannot be increased. On the other hand, if it is less than 0.1 μm, a large amount of water is required to prepare the sludge, resulting in a decrease in productivity.

[0014]

【Example】

(Example 1) 80% by weight of alumina powder having an average particle size of 0.4 to 0.5 μm and 20% by weight of ρ-alumina having an average particle size of 2 μm
Pure water (20 parts by weight) and a polycarboxylic acid ammonium salt (trade name: SN Dispersant 5468) as a dispersant were mixed with 100 parts by weight of the inorganic powder consisting of, and the slurry was prepared using an alumina pot mill. Table 1 shows the amount of polycarboxylic acid ammonium salt added and the viscosity of the slurry.

[0015]

[Table 1]

Among them, the slurry No. 3 having a low viscosity is used, and the rod shown in FIG. 1 is injected with a plunger type injection molding machine to obtain an injection pressure of 20 kgf / cm ² and a plunger temperature of 20.
Molded at a mold temperature of 60 ° C. Flexural strength of the molded body is 40 kgf / cm ^2, the flexural strength after drying of 40 hours was 100 kgf / cm ^2. This is from room temperature to 1600 ℃
The temperature was raised in 4 hours and the temperature was maintained at 1600 ° C. for 1 hour to obtain a ceramics sintered body. After the furnace was cooled, the sintered body was taken out and its surface was examined. No swelling or cracking was observed.

Example 2 Average particle size 0.4 to 0.5 μm
Of 40 to 98% by weight of alumina powder and ρ having an average particle diameter of 2 μm
20 to 40 parts by weight of pure water and 100 parts by weight of inorganic powder consisting of 60 to 2% by weight of alumina, and 0.4 parts by weight of ammonium polycarboxylic acid salt (trade name SN Dispersant 5468) as a dispersant, The slurry was prepared using an alumina pot mill. Using a plunger type injection molding machine, injection pressure 20kgf / cm ² , mold temperature 60
It shape | molded under (degreeC) and measured the bending strength of the molded object. The results are shown in Table 2.

[0018]

[Table 2]

When the content of ρ-alumina was less than 3% by weight, the molded body was not cured, and when the content of ρ-alumina was more than 50% by weight, the composition was too fast to be molded. Than this,
The amount of ρ-alumina added is 3 to 50% by weight, preferably 1
It can be said that the range of 0 to 30% by weight is appropriate.

Example 3 Average particle size 0.4 to 0.5 μm
Of 100% by weight of inorganic powder consisting of 80% by weight of alumina powder and 20% by weight of ρ-alumina having an average particle size of 2 μm.
0 parts by weight, polycarboxylic acid ammonium salt (trade name SN
Dispersant 5468) 0.4 part by weight was added, and the slurry was prepared using an alumina pot mill. Using a plunger type injection molding machine, this sludge was injected at an injection pressure of 10 kgf / cm ² , a plunger temperature of 20 ° C., and a mold temperature of 25.
A molded body having the shape shown in FIG. 1 was molded at ℃. This slurry did not cure even if held in the mold for 1 hour, and a molded body could not be obtained. This is because the amount of pure water was too large and the slurry did not harden.

Example 4 100 parts by weight of an inorganic powder composed of 90% by weight of zirconia having an average particle size of 0.5 μm and 10% by weight of ρ-alumina having an average particle size of 2 μm, 20 parts by weight of pure water and sodium polycarboxylic acid salt. (Commercial name Nopcos Perth 44-C) A slurry containing 1 part by weight was prepared with an alumina pot mill, and the slurry was injected with a plunger type injection molding machine at an injection pressure of 20 kgf / cm ² , a plunger temperature of 20 ° C., and a gold temperature. The shaped article shown in FIG. 1 was molded at a mold temperature of 60 ° C. The bending strength of this molded body was 20 kgf / cm ² , and after drying, the temperature was raised from room temperature to 1600 ° C. in 4 hours, and
Hold at 600 ° C. for 1 hour. When the surface of the fired body was examined after being taken out after cooling in the furnace, no swelling or cracks were observed, and a good ceramics sintered product was obtained.

[0022]

EFFECTS OF THE INVENTION According to the method for producing a ceramic molded body using sludge containing ρ-alumina of the present invention, since the sludge has very good fluidity, molding defects such as welds and flow marks do not occur. Since the organic binder is not included, the degreasing step is unnecessary, the manufacturing process is simplified, and the manufacturing time is greatly shortened. Furthermore, by using sludge with good fluidity, it is possible to mold at a low injection pressure. Therefore, the size of the injection molding machine can be reduced, and the mold used is aluminum and its alloys, resins, wood, etc. Lightweight materials can be used.

According to the method for manufacturing a ceramic molded body of the present invention, it is possible to easily manufacture a complicated and homogeneous molded body having no density unevenness, and it is possible to manufacture a complex shaped product or a thick product with high dimensional accuracy. It is a thing.

[Brief description of drawings]

FIG. 1 is a front view of a rod manufactured in an example of the present invention (A).
It is a side view (B).

Front page continued (72) Inventor Nobuo Takase 150 Nikamicho, Takaoka-shi, Toyama Prefecture Toyama Industrial Technology Center

Claims (3)

[Claims] 1. 50 to 97% by weight of ceramic powder, ρ
Inorganic powder 100 consisting of 50 to 3% by weight of alumina powder
A method for producing a ceramic molded body, which comprises mixing 15 to 50 parts by weight of water with parts by weight to form a slurry and subjecting the slurry to a non-absorption type heated to 30 to 100 ° C. 2. The ceramic molded body according to claim 1, wherein a polycarboxylic acid-based, polyphosphoric acid-based, naphthalene sulfonic acid-based, amine-based or allyl sulfonic acid-based dispersant is added to the slurry. Manufacturing method. 3. The particle size of the ρ-alumina is 0.1-10 μm.
The method for producing a ceramic molded body according to claim 1, wherein m is m.